ABCNews.com(MIDLAND CITY, Ala.) -- A brother and sister who escaped the school bus where a 5-year-old autistic boy was taken hostage by a retired Alabama trucker are speaking out about the standoff and the man who threatened the lives of the children on board.

"I look up and he's talking about threatening to kill us all or something," 14-year-old Terrica Singletary told ABC's Good Morning America. "He's like, 'I'll kill all y'all, I'll kill y'all, I just want two kids.'"

Singletary and her brother, Tristian, 12, said Jimmy Lee Dykes boarded the bus on Tuesday and offered the driver what appeared to be broccoli and a note, before demanding two children.

"The bus driver kept saying, 'Just please get off the bus,' and [Dykes] said, 'Ah alright, I'll get off the bus," said Terrica Singletary, "He just tried to back up and reverse and [Dykes] pulled out the gun and he just shot him, and he just took Ethan."

School bus driver Charles Albert Poland Jr., 66, was fatally shot several times by Dykes.

The siblings and the rest of the students on board were able to get away unharmed, but were shocked by what had transpired on Tuesday afternoon.

"I never thought I would have to go through a shootout," Singletary said.

They said they had seen Dykes, 65, working on his fence, and described him as a menacing figure.

"He was very protective of his stuff," Tristian Singletary said. "Whenever he stares at you, he looks kinda crazy."

Dykes has been holed up in his underground bunker with his 5-year-old hostage named Ethan near Midland City, Ala. for five days now. Neighbors told ABCNews.com that Dykes has been known to retreat underground for up to eight days.

While Dykes, who was described as having "no regard for human life," has allowed negotiators to send Ethan's medicine, as well as coloring books, into the bunker for the boy through a ventilation pipe that leads into the 6 by 8 foot subterranean hideout 4 feet underground, authorities are staying quiet about their conversations with Dykes.

Meanwhile, his peers are steadfast that he will return home soon.

"Ethan will make it out there, Ethan will make it out there," said Tristian Singletary.